1. Field of the Invention
The present invention relates to a thermal printer, and more specifically, to a thermal printer provided with a plurality of recording units along a carrying path of a long recording medium.
2. Description of the Related Art
Conventionally, a thermal printer is known, which records an image on a recording medium using a plurality of ink ribbons on which different colors of ink are coated respectively. In the thermal printer, a plurality of thermal heads provided corresponding to the respective ink ribbons transfers ink of the respective ink ribbons onto the recording medium to record a desired image on the recording medium. Such a thermal printer has a plurality of ink ribbons, on which multiple colors (for example, cyan (C), magenta (M), and yellow (Y)) of ink and transparent overcoat (OP) ink are respectively coated, and a plurality of thermal heads corresponding to the number of the ink ribbons. These thermal heads are arranged at predetermined intervals along a carrying path of the recording medium, each of the thermal heads being disposed to oppose the recording medium with the ink ribbon interposed therebetween. At a position opposite to each of the thermal heads, a platen is provided with the ink ribbon and the recording medium interposed therebetween.
In the thermal printer, a first thermal head, a second thermal head, a third thermal head, and a fourth thermal head are disposed in the above-mentioned order from the most upstream side in the carrying direction of the recording medium. If a recording-starting position of the recording medium reaches a position opposite to the first thermal head, the first thermal head is pressed against a first platen opposing the first thermal head. Specifically, the first thermal head is made to be down toward the first platen opposing the first thermal head or the first platen is made to be down toward the first thermal head. Then, the first thermal head is pressed against the first platen with the recording medium and the ink ribbon interposed therebetween, so that ink (C), for example, is transferred onto the recording medium by the first thermal head.
Subsequently, if the recording-starting position of the recording medium reaches the position opposite to the second thermal head, the second thermal head is made to be down or the second platen opposing the second thermal head is made to be down. Then, the second thermal head is pressed against the second platen with the recording medium and the ink ribbon interposed therebetween, so that ink (M) is transferred by the second thermal head.
As such, the thermal heads are made to be down sequentially from the upstream thermal heads in the carrying path of the recording medium or the platen are made to be down sequentially from the upstream platen to transfer ink onto the recording medium. Then, a desired color image is recorded on the recording medium with a plurality of colors of ink (for example, refer to Patent Document 1).
A printer as a conventional thermal printer provided with a front tension roller on the downstream side of each of multiple thermal heads is proposed (for example, refer to Patent Document 2).
A printer as a conventional thermal printer is proposed, of which a carrying path is bent in each position of a capstan roller and a plurality of thermal heads so as to project into a pinch roller and a platen (for example, refer to Patent Document 3).
A printer as a conventional thermal printer is proposed, in which the slack is formed between a plurality of thermal heads (for example, refer to Patent Document 4).
[Patent Document 1] U.S. Pat. No. 6,474,886
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2003-231318
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 2001-246769
[Patent Document 4] Japanese Unexamined Patent Application Publication No. 09-156142
However, in the conventional thermal printers, there is a problem in that they cannot meet the needs of high performance with the improvement of recording quality for recent years.
For example, if the second thermal head is pressed against the platen with the recording medium interposed therebetween on recording on the recording medium by the first thermal head, deviation in recording of the first thermal head occurs due to the impact onto the recording medium which is caused by the pressing operation.
In other words, in the conventional printers, disturbances generated on the downstream side between the respective thermal heads propagate through the recording medium toward the upstream side, which results in deteriorated recording quality.